Download HW 1 - Pomona College

Tahir Andrabi
Economics 154
Fall 2004
Homework 1
Due Wednesday, September 29
Watson, Chapter 2, Q. 1, 2
Watson Chapter 3, Q. 2, 3
Watson Chapter 4, Q. 3
Watson Chapter 7, Q. 3
Gibbons, Problems 1.2, 1.8
I)
The following problem is based on a version of the tragedy of the commons.
There is a common grazing ground in the middle of a town. Each individual has to decide how
much grass to let his goats eat in the commons.
His utility function (if there are n total players) is as follows:
Ui
=
B (gi ) - C (g1,g2 ,g3 ,.. , gi ,.. gn)
where g1 is the amount of grass grazed by the player 1’s goat.
There are private benefits but the costs are interdependent.
A specific functional form could be
B (gi )
=
C (g1,g2 ,g3 ,.. , gi ,.. gn) =
gi
(1/2)[ gi + (1/2) (g1 + g2 + g3 +..+ gi-1 + gi+1 +.. + gn)]2
so that
Ui
=
gi - (1/2)[ gi + (1/2) (g1 + g2 + g3 +..+ gi-1 + gi+1 +.. +
gn)]2
The first term is the benefit to the individual of the grazing. The second term (the squared one) is the
costs to the individual of the grazing. Each individual faces his direct cost of grazing, and half of the
other persons’ grazing costs. The costs are nonlinear.
The particular functional specification: i. e the squared costs, and why the other guys grazing imposes
half a cost on the first person is done for guaranteeing a solution, algebraic ease, and stability of the
model.
For a two player game, this translates to
Ui
=
g1 - (1/2)[g1 + (1/2) (g2)] 2
i)
ii)
iii)
Specify the best responses for the n-players game.
Solve for the private and the social optimum.
Comment on the nature of the externality as n varies.
II) If the standard battle of sexes were a sequential game instead of a simultaneous one, is there a first
mover advantage?
Now suppose we have a battle of the sexes game as in Gibbons, page 11, but with a modification.
The man would still prefer to go to the fight, and the woman to the ballet, but now what is more
important to them is that the man wants to show up at the same event as the woman, but the
woman wants to avoid him.
i)
Construct a game matrix to illustrate this game, choosing numbers to fit the preferences
verbally.
ii)
What is the Nash equilibrium if both players move simultaneously.
iii)
If the woman moves first, what will happen?
iv)
Is there a first-mover advantage? Is there a first mover advantage in the standard battle of
sexes?
III) A. What is the unique Nash equilibrium in the game where two player simultaneously have to
choose a number
i) in the space [0,N]and the payoffs to each are number of dollars equal to the product of the two
numbers?
ii) in the space [0,) and the payoffs to each are number of dollars equal to the product of the two
numbers?
B. What is the Nash equilibrium in a game where one is supposed to:
i) Guess 1/3 the average of what everybody else in the class is guessing. (The range is 0 to 100)
IV) Comment and give an example:
Presence of spillovers is enough to show that there is strategic interdependence.
V) Finish the numerical example from the paper by Bulow-Klemperer. (Show what happens when the
price in the first market goes to 55.)
VI)
This is a typical labor-leisure problem in economics but now with a game theoretic twist.
Each person has to decide between choosing how to allocate her waking hours between leisure and labor.
Labor is tiresome and gives you disutility while leisure has intrinsic positive utility. However, labor earns
you wages at some rate with which you can buy stuff that gives you positive utility.
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Now the game theoretic twist: Think of a two-person community, in which the utility of one person’s
leisure depends on how much leisure the other person decides to take. Disutility from work and the
wages earned is independent of the other person’s decision.
i)
How would you formalize this decision-making problem for each person?
What do you think is the nature of the interdependence here. Think both in terms of spillovers
and strategic interdependence.
Try out some functional forms for the interdependence.
ii) Now suppose the wage rate for one of the persons goes up. i. e. opportunity cost for his labor
goes up. What happens to the leisure taken by the other person?
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